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commercial copper and do not modify its properties appreciably, provided their
amount does not exceed 0-3-0-4%.

Compositions of the commoner commercial coppers are given in Table XXI
(Hollard, Schnabel, Hampe).


Phosphor-copper is usually employed as a deoxidiser and for the prepara-
tion of phosphor bronzes. It. occurs mostly in cakes of metallic appear-
ance and bronze or steel-grey colour and sometimes with bluish reflections ;
it is brittle and has a crystalline structure.

Its analysis comprises essentially determinations of the phosphorus
and copper. The impurities, derived from those of the copper used in its
preparation, may be estimated by the methods given on p. 214 for the
analysis of commercial copper.

1.  Determination of the Phosphorus.0*5 gram of the finely pow-
dered sample are treated in a covered dish with 10 c.c. of nitric acid (D 1-4),
gentle heat being applied when the action slackens.    If any unattacked
metal remains after about 30 minutes, a few drops of hydrochloric acid
are occasionally added and the liquid heated until solution is complete
and then evaporated to dryness with 10 c.c. of nitric acid.    The residue
is extracted with hot water acidified with nitric acid and the liquid filtered
to separate (and determine, if necessary) any traces of  silica present, the
nitrate being made up to 250 c.c.

50 c.c. of this solution are evaporated to 10 c.c. and treated with
150 c.c. of ammonium molybdate solution, the remaining procedure being
as in the determination of phosphorus in iron (q.v.).

2.  Determination of the Copper.i gram of the sample is treated
with 10 c.c. of nitric acid (D 1-2) and 5 c.c. of hydrochloric acid in a covered
beaker.   The solution is evaporated with 2-3 c.c. of sulphuric acid until
the nitric and hydrochloric acids are completely expelled and then heated
on a sand-bath until white fumes of sulphuric acid appear.    When cool
the residue is taken up in hot water, the solution being mixed with 5-6 c.c.
of nitric acid (D 1-4), made up to 200-250 c.c. and electrolysed (see p. 214) :
Winlder electrodes ; ND100 = 0-3-0-4 amp. ; duration = 10-15 hours.

Phosphor-copper usually contains 9-15% P (sometimes, however, only 0-5-
5%). Preference is given in practice to products with 10% P.


Cupro-silicon or copper silicide, also improperly termed silicon bronze,
is prepared in the electric furnace by reducing silica with carbon in presence
of copper. It is used especially for the deoxidation of brasses and bronzes
and for the preparation of copper-silicon alloys containing small quantities
of silicon and used in electro-technics for telephone wires, cables, etc. (alloys

with 0-2-3-5% Si).

Its analysis  comprises   essentially determinations  of  the silicon andders it cold short if present in greater quantity